Numerous types of valve assemblies are known in the prior art. Prior art valve assemblies are used in a variety of environments generally to perform the function of controlling the flow of a gas, liquid or a solid through a conduit. U.S. Pat. Nos. 3,291,443 to Schulz et al. and 3,640,499 to Jung disclose valve mechanisms wherein a rotatable valve member is disposed within a flexible walled conduit. In Schulz et al., the flexible conduit forms a portion of the overall flow conduit. In Jung, the flexible walled conduit is formed as an insert within an overall flow conduit. Neither Schulz et al. nor Jung are designed as discharge valve assemblies for use in dust or particulate material collection systems. Also, the valve members are pivotable about axes passing through the valve members and through a line bisecting each respective valve member. When such pivot axes are used, the stretching or distortion of the flexible conduit during the opening and closing of the valve member is minimized.
An article by Michael Hussey entitled "Valves and Air Locks for Industrial Dust Filter Systems" in the September/October, 1976 issue of Filtration and Separation provides a summary of various types of valve assemblies used in dust filtration systems. As disclosed within the Hussey article, numerous type of valve assemblies are used in dust filtration systems. Such valve assemblies include slide valves, diverter valves, pinch valves, single and double flap valves, flexible blade rotary valves and floating seal rotary valves.
Multiple-stage dust collectors and in particular multiple-stage dust collectors for use in mine drilling operations are known in the prior art. In modern underground mining operations the method of supporting the mine roof by beams extending from floor to roof has been replaced by a method in which the roof is bolted to strata above the roof. Holes are drilled through the roof and into the supporting strata. Bolts are then utilized to secure the roof to the supporting strata. Large quantities of dust are generated in the roof drilling operation. It is desirable to move the generated dust from the roof drill operator environment. In addition to improving the operator environment, dust removal increases roof drill performance.
The prior art includes a number of multiple-stage roof drill dust collectors developed by the assignee of the present invention. One such multiple-stage collector is described in "Operation Manual for Donaldson Roof Drill Dust Collector RDXOO-4545" printed by the Donaldson Company, Inc. in 1975. Another multiple-stage dust collector is disclosed in U.S. patent application Ser. No. 805,986, now U.S. Pat. No. 4,144,043 assigned to the assignee of the present application. The dust collectors described in the above publication and application include first stage cyclone separators, second stage separators, and third stage filters. One of the second stage separators includes reverse-flow cyclone separator tubes, while the other second stage separator includes a side outlet separator.
In the above-described prior art dust collectors, the roof drilling operations must be periodically stopped while the collected dust is removed from chambers within the multiple-stage dust collectors. Dust collection chambers are located below at least the first and second stages of such a multiple-stage dust collector. The dust collection chambers must be manually cleaned periodically. So that the mine drilling operation can be carried out efficiently without the need of frequently cleaning the dust collection chambers, the dust collection chambers have been made of a relatively large capacity, for example 1.3 to 2.4 cubic feet. The requirement of a large collection capacity within the dust collection chambers increases the overall size of a dust collector. However, to increase size of the dust collectors, while at the same time maintaining dust collection efficiency, is not cost effective. Furthermore, the maximum size of a multiple-stage dust collector housing is limited by the fact that it must be conveniently mounted on the roof-drill vehicle and the more compact a roof-drill vehicle can be made increases the versatility of such a vehicle within mining operations.